Printers are useful for producing printed images of a wide range of types. Printers print on receivers (or “imaging substrates,” “media,” or “recording media”), such as pieces or sheets of paper or other planar media, glass, fabric, metal, or other objects. Printers typically operate using subtractive color: a substantially reflective receiver is overcoated image-wise with cyan (C), magenta (M), yellow (Y), black (K), and other colorants. One common type of printer is a printing press that uses inkjet print engines to deposit CMYK inks on a receiver web. A separate marking unit can be used to deposit each color of ink, and the marking units can be arranged in series along the path of the receiver.
The speed of a web-fed inkjet printing press is limited by the drying time of the ink. Between the time an ink drop reaches the media and the time the image side of the media next comes into mechanical contact with a member such as a roller, enough of the solvent in the ink should dry so that ink is not inadvertently transferred to the member. Cut-sheet system, e.g., the HP DESKJET 500C, hold wet paper above the output stack on side guides for a selected dwell time before dropping the sheet on the stack. However, this scheme is not applicable to web presses. Moreover, even in cut sheet presses, it is desirable to maintain a high throughput of pages (large number of pages per minute). Drying time between the printing of one sheet and the printing of the next sheet reduces productivity.
A large number of schemes, e.g., U.S. Pat. No. 8,053,044 to Zhou et al., provide special media that more readily absorb ink or otherwise assist in drying. However, each media type has a certain maximum speed in a given printer. For example, some glossy stock should be printed more slowly than matte stock, since glossy stock does not absorb ink as quickly. It is desirable that customers be as unconstrained as possible in their choice of media, and be able to run media at high print speeds. Moreover, a print shop running both multiple types of presses would prefer not to stock and manage large numbers of different types of media.
Various printers use multiple dryers to dry the web, e.g., the KODAK VERSAMARK DS3700. U.S. Pat. No. 7,207,670 to Silverbrook et al. describes a dryer with an integral media path (col. 29) in which the media hang down in the dryer to form a partial loop while drying. U.S. Patent Publication No. 2011/0199414 by Lang describes idler rollers that contact a second, non-image side of the web until liquid ink on the first, image side of the web has dried or hardened. Moreover, high-thermal-flux drying of clay-coated papers can result in paper blistering when moisture in the paper boils off from under the clay coating. Drying can also heat ink, especially black ink, to a temperature at which the paper around the ink burns off. U.S. Patent Publication No. 2011/0043585 by Silverbrook et al. describes a printer in which distances between print zones, and total length of the media path, are restricted. U.S. Patent Publication No. 2009/0189929 by Motojima et al. describes a zig-zag web path with printheads at each step.
However, these systems still use active dryers. Dryers can require a significant amount of power and floor space. Dryers can damage the paper, as discussed above. Moreover, any drying stage can affect the dimensions of the paper, as described in U.S. Patent Publication No. 2011/0102851. Drying can affect media dimensions unpredictably, since the changes depend on the initial moisture content of the media, the ink laydown and pattern, and the environmental conditions. Dimensional changes can cause mis-registration between images printed sequentially on opposite sides of a web. Moreover, drying between marking units that mark on the same side of the receiver can cause color-to-color mis-registration.
There is a continuing need, therefore, for a way of drying a web with reduced power consumption, reduced footprint requirements, improved registration, and reduced thermal shock of, and damage to, the print media.
Reference is made to WO 201097117, the disclosure of which is incorporated herein by reference.